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Review Essays of Academic, Professional &
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Nematode Behaviour by Randy Gaugler, Anwar L. Bilgrami (CABI Publishing)
Netamode worms are among the most ubiquitous organisms on earth. They include
free-living forms as well as parasites of plants, insects, humans and other
animals. Netamode behavior is a key issue in understanding of these ways of life
or parasitic relationships. This book provides a unique,
comprehensive review of current knowledge of the behavior of netamodes. All of
the key topics such as locomotion and orientation, feeding and reproductive
behavior, and biotic and abiotic interactions are reviewed. Written by leading
authorities from the USA, UK, India and New Zealand, it brings together a wide
range of disciplines and will attract a broad readership.

In the absence of well-defined criteria, behavioural
classification of nematodes based upon their activities and adaptations becomes
a difficult task. At what point do nematodes sense physical and chemical
stimuli? Is the ingestion of food by nematodes passive or active? What type of
behaviour do nematodes show when sperm are released? Many similar questions
could be addressed if a classification system of nematode activity based on
endogenous and exogenous, and biotic and abiotic components was adopted.

Nematodes display behaviours as coordinated and interacted
responses. This is why behaviour in such deceptively simple organisms as
nematodes is complex. Nematodes use receptors, the central nervous system, and
somatic musculature to perform exogenous activities (e.g. locomotion), whereas
the sympathetic nervous system, changes in body turgor pressure and somatic
muscles are used to accomplish endogenous activities, such as ingestion and
defaecation.

Behaviours may be classified into two basic types:
operational (voluntary) and consequential (influenced by stimuli). Behaviour by
operation refers to what nematodes do and describes exogenous or endogenous
activities such as movement, hatching, vulval contractions, stylet movement,
etc. Classification by operation brings behavioural patterns of similar
spatio-temporal organizations into a single group, including body postures, wave
patterns, movements in egg, muscular movements during defecation, swarming,
nictation, orientation and penetration. It is simple in some cases (e.g.
determining the number of muscles involved in coordinating a particular
activity) but difficult where patterns are mixed and complicated, for instance,
the different movements involved in single types of behaviour such as
orientation, feeding or copulation. Various subcomponents such as crawling,
forward and backward movements, coiling, sideways movements, lateral head
movements, and head and tail movements may be considered to simplify such
classification.

Behaviour by consequence is extremely varied, since
nematodes are governed by various endogenous activities and sensory stimuli of
physical and chemical natures. Changes in behaviour due to chemical (e.g.
kairomones, allomones, sex pheromones) or physical (e.g. temperature, moisture,
electricity, evasive actions taken to avoid predation) stimuli are examples of
behaviour by consequence. Description of behaviour by consequence brings clarity
in experiments, distinguishes different types and reduces experimental error.
Behaviour by consequence can take several forms. First, chemical and physical
stimuli are information-generating patterns (e.g. movement patterns). Next,
modes of triggering stimuli and actions of the nervous system constitute
muscular, neurological, and/or physiological mechanisms. These mechanisms
present displays which constitute behaviours.

Information on behavioural adaptations to diverse
ecological conditions is assembled and discussed by Gregor Yeates in Chapter 1
('Behavioural and Ecological

Locomotion is fundamental to nematode behaviour and impacts
feeding, food finding, mating and migration. Nematodes move by undulatory
propulsions as described in detail by Burr and Gans (1998) and Alexander (2002).
Locomotion includes crawling or swimming through leaf surfaces, stomata, root
hairs and tissues, rotting plant matter, water, excreta, intestinal microvilli,
animal tissues, blood vessels and insect tracheae. Nematodes may also
accelerate, stop, reverse, turn, omega-turn, probe, orient, swim, burrow,
penetrate, poke, lace, climb, bridge, roll, graze, cruise, nictate, aggregate,
swarm, ambush, hitchhike, loop or somersault. Although nematodes cannot fly,
infective juveniles of some entomopathogenic species nearly accomplish this feat
by leaping distances of nine body lengths when in the presence of an insect
host. These fascinating aspects of nematode locomotion are explored by Jay Burr
and Forest Robinson in Chapter 2 (`Locomotion Behaviour'). This chapter details
the various types of loco-motion, the role of the hydrostatic skeleton and
neuromuscular control in locomotion. The authors explain how movements are
achieved and controlled, how propulsive forces are generated against external
substrates, what role neuromuscular system plays, how locomotion is adapted in
different environments, and what alternate means are involved in locomotion when
undulatory propulsion is absent. The authors elucidate functions of
neuromuscular structures associated with nematode locomotion. They discuss the
fine points of body wall structure, elastic properties, lateral connection to
cuticle, tonus and development of bending muscles. Transmission of forces during
locomotion, the functions of synapses, neurotransmitters, and neuromodulators,
the propagation of waves, the mechanism of orientation and factors generating
frictional resistance are discussed. The authors emphasize the need to study
mechanical properties and putative functions of the hydrostatic skeleton,
inflation pressures, change in dimensions, crossing angle, elasticity, cuticle
ultrastructure and bending. There is a strong need for more integrative
investigations on locomotion based on comparative structural, functional and
behavioural diversities with reference to nematode adaptations. Of special
interest is the promise of novel methodologies, particularly video capture and
editing (VCE) with microscopy (De Ley and Bert, 2002) to archive nematode
locomotion for in-depth analysis of the mechanisms involved.

Nematodes receive and interpret signals from the
environment and from each

other that allow them to find hosts, mates, develop and
survive. Ekaterina Riga uses Chapter 3 ('Orientation Behaviour') to describe
various facets of nematode orientation behaviour by discussing types of stimuli
and mechanisms involved in nematode chemo-, mechano-, photo-, thigmo- and
thermo-tactic responses. The functional aspects of receptors are discussed in
relation to their role in orientation. Riga suggests that novel control
methodologies could develop by disrupting certain phases of the nematode life
cycle (e.g. phases during search for food or mates) (Perry, 1994). As
hypothesized by Bone and Shorey (1977), such disruptions might be achievable by
saturating the nematode's soil environment with artificial pheromones or host
cues. Bone (1987) and Perry (1994) have specifically suggested that nematode
reproduction could be disrupted using the sex pheromone confusant method.
Further studies are needed to understand the role and functions of receptors in
nematode orientation.

Comprehensive knowledge about food and feeding habits is
fundamental to understanding aetiology. Anwar Bilgrami and Randy Gaugler's
Chapter 4 ('Feeding Behaviour') focuses on patterns of feeding types and
mechanisms, muscular movements, food and feeding habits, extracorporeal
digestion, host recognition, host tissue penetration, prey catching,
cannibalism, ingestion and defecation. A central theme is that despite
remarkable structural and functional similarities, nematodes show great
diversity in food and feeding habits, obtaining nutrients from bacteria,
protozoa, fungi, algae, other nematodes, or plant and animal tissues. They may
be monophagous or polyphagous with some species even showing dual or biphasic
feeding habits (Yeates et al., 1993), switching food resources at different
stages of the life cycle. This diversity, coupled with the disparate nature of
the disciplines that work with plant, animal, insect and free-living nematodes,
has complicated nematode characterization into different feeding groups.

The structure of feeding organs predicts a nematode's food
and feeding habits (Bird and Bird, 1991). These structures may differ between
nematode groups but they perform the same functions of feeding and ingestion.
The feeding apparatus can be categorized into engulfing (e.g. predatory
mononchs), piercing (e.g. plant-parasitic, predatory and fungal feeding),
cutting (e.g. predatory diplogasterids, some marine and animal-parasitic
nematodes) and sucking types (e.g. bacterial feeding and some animal-parasitic
nematodes). Plant and fungal feeders and some predatory nematodes possess a
needle-like stylet for piercing tissues. Plant-parasitic triplonchids and
predatory nygolaims wield a solid pointed tooth, whereas preda-tory mononchs,
diplogasterids and monohysterids have buccal cavities with wide openings and
specialized structures such as dorsal tooth, ventral teeth and denticles. The
subventral lancet, cutting plates, dorsal gutter and dorsal cone are structures
associated with animal-parasitic nematode feeding. These structures perform
similar functions, i.e. piercing, penetration, cutting food resource and
ingestion of nutrients.

1990) are reviewed by Bilgrami and Gaugler in Chapter 4.
The authors divide nematode feeding into six major components – structure and
function of feeding apparatus, feeding types, food search, food capture,
post-feeding activities and food preference – by adopting a scheme of
classification based on nematode food and feeding habits. Explanations on the
role of extracorporeal digestion of nutrients prior to ingestion, formation of
tubes and plugs during feeding, and extra-intestinal food absorption provide a
better understanding of adaptive processes during nematode feeding.

There is greater variation in nematode reproductive biology
than any other aspect of their behaviour. Robin Huettel discusses this diversity
in Chapter 5 ('Reproductive Behaviour'), including evolutionary and ecological
aspects. How nematodes respond to sex pheromones and what behavioural mechanisms
are adopted during mating are among the subjects treated. Sensory habituation,
influence of age, sexual status, physical and chemical factors on orientation,
recognition and copulation are also considered. Sex pheromone activity in
Heterodera glycines females has been attributed to vanillic acid (Jaffe et al.,
1989). Bioassays such as lactin binding are used to study chemotactic responses
of H schachtii males to female sex pheromones (Aumann et al., 1998). Aumann and
Hashem (1993) extracted attractive substances from females of H. schachtii which
possess pheromone activity for males. Greet and Perry (1992) reviewed patterns
and evolution of sexuality, genetic basis of sex determination, sexual behaviour
and differentiation, the role of sex attractants, spicule function and
copulation behaviour in nematodes. The cellular basis of chemotaxis, thermotaxis
and developmental switching may be studied in nematodes by killing selected
neurones with laser ablation and assaying effects on behaviour. Ablation is a
powerful but underutilized tool that may be applied to study diverse functions
of the nervous system and the cellular basis of specific nematode behaviours.

Ageing has been defined as a time-dependent series of
cumulative, progressive, intrinsic and deleterious functional and structural
changes that begin to manifest at reproductive maturity, eventually culminating
in death (Arking, 1999). Ageing affects locomotion, fecundity, oviposition,
vulval contractions, sexual attraction, copulation, osmotic fragility and
feeding activities of nematodes (Zuckerman et al., 1972; Gems, 2002; Herndon et
al., 2002). Ed Lewis and E.E. Pèrèz in Chapter 6 (Ageing and Developmental
Behaviour') describe age-dependent nematode behaviour during development and
after reaching adulthood. Learning processes in nematodes are non-associative
but are involved in the modification of behaviour due to repeated exposure to a
single or multiple cues, e.g. habituation and sensitization (Bernhard and van
der Kooy, 2000). Chapter 6 is made more interesting when the authors explain
learning processes in nematodes and correlate this with ageing. Our
understanding of ageing behaviour has made a deep breach at the genetic and
molecular levels using C. elegans as a model organism (Gershon and Gershon,
2001). However, studies on ageing behaviour of other groups of nematodes have
been neglected. In this chapter, the authors suggest several lines of research
on ageing behaviour in other important nematode species based upon
accomplishments with C. elegans. These could prove useful in the development of
novel management practices, and in monitoring environmental pollution using
nematode behavioural parameters as bioindicators.

Denis Wright brings together the scattered information on
behaviour as it relates to waste and ionic regulation in free-living and
parasitic nematodes in Chapter 7 (`Osmoregulatory and Excretory Behaviour').
Earlier reviews emphasized the molecular cell biology of animal-parasitic
species (Thompson and Geary, 2002). Nematodes regulate water content to adapt to
changing osmotic conditions (Wright, 1998). Failure to do so may disrupt
locomotion because of the anisometric nature of the cuticle (Wright and Newall,
1980). Osmotic factors also govern nematode survival (Glazer and Salame, 2000),
freezing tolerance (Wharton and To, 1996), hatching (Perry, 1986), reproduction
(Gysels and Tavernier-Bracke, 1975) and feeding (Raispere, 1989). The nematode
excretory system has been described as a `secretory—excretory' system (Wright,
1998) because of its dual role in osmoregulation and excretion. Chapter 7
integrates the two mechanisms so as to explain changes in nematode behaviour
occurring due to osmotic stresses and excretion of nitrogenous waste products.

Behavioural responses are the result of intrinsic and
extrinsic stimulations involving various physiological and biochemical
activities. Roland Perry and Aaron Maule in Chapter 8 (`Physiological and
Biochemical Basis of Behaviour') describe how these activities play a huge role
in regulating nematode behavioural responses. Physiology and biochemistry
influence functions of sense organs, cuticle, muscles, glands, digestive and
excretory organs associated with nematode behaviours. Correlations with
physiological and biochemical factors have been established with sensory
responses (Perry and Aumann, 1998), female sex pheromones (Aumann et al., 1998)
and starvation in nematodes (Reversat, 1981). Results on chemosensory responses
suggest each receptor cell in the amphids detects different chemicals. A
promising approach to investigate chemosensory responses would be to identify
and analyse attractants and repellents in the natural environment, and test them
for independence. Chapter 8 further describes the role of hormones and enzymes
during behaviour including ecdysis, extracorporeal digestion, salivation,
hunger, chemoattraction, nerve conduction, dauer formation, population
regulation and sex attraction. Chemical neurotransmitters play an important role
in nematode behaviour (Sulston et al., 1975; Wright and Awan, 1976). Willet et
al. (1980) considered the nervous system in nematodes as cholinergic, with
acetylcholine and y-aminobutyric acid as excitatory and inhibitory transmitters
respectively. Vaginal and vulval movement in C. elegans, Aphelenchus avenae and
Panagrellus redivivus are controlled by serotonin, 5 hydroxytryptophan and
adrenaline (Croll, 1975). It is not difficult to study nematode behaviour in
relation to neurones as their numbers do not exceed 250 (Willet et al., 1980).
Neurones that mediate behavioural responses to different chemicals have been
identified through laser ablation (Troemel, 1999). Genetic and molecular studies
on nematode behaviour have indicated involvement of G protein signalling
pathways in chemotransduction. Nematodes (e.g. C. elegans) are estimated to use
approximately 500 chemosensory receptors to detect a large spectrum of chemicals
in the environment. Unfortunately, the physiological and biochemical bases of
nematode behaviour are

less developed than the rapidly expanding knowledge on the
molecular aspects of behaviour, yet Chapter 8 takes a molecular approach to
securing a broader perspective on biochemical and physiological aspects of
nematode behaviour.

Genes control behaviour and molecular genetics has become a
powerful new tool to study nematode behaviour. Maureen Barr and Jinghua Hu in
Chapter 9 (Molecular Basis for Behaviour') make a novel effort to describe
various aspects of behaviour at the molecular level using C. elegans as their
model. Laser ablation experiments have revealed important similarities in C.
elegans with visual and olfactory transductions in vertebrates (Mori and
Ohshima, 1997). Movement and migration have been analysed theoretically
(Anderson et al., 1997a) and experimentally (Anderson et al., 1997b). The role
of ageing, acetylcholinesterase, motor neurone M3 and genes in regulating C.
elegans behaviour has been established. Studies on neural G protein signals show
that EGL-10, RGS-1 and RGS-10 pro-teins alter signals in C. elegans to induce
nematode behavioural responses. Oviposition is regulated by the FLP-1 peptide
(Waggoner et al., 2000) and reversals in foraging movements are controlled by
small subsets of neurones (Zheng et al., 1999).

Most nematodes live in the soil, an environment heavily
colonized by other organisms. Nematodes interact with this biotic community and
adapt to survive, adaptations that often have behavioural components. How
nematodes interact with beneficial and antagonistic organisms including
intraspecific interactions, what causes interactions to occur, and how these
interactions affect nematode behaviour constitute the subject of Chapter 10
(Biotic Interactions') by Patricia Timper and Keith Davies. This chapter
describes different types of interactions, e.g. phoresy, antagonism, mutualism,
commensalism and amensalism, with reference to behaviour. The authors draw
particular attention to the extraordinary behaviours shown by nematodes in
phoretic associations. Phoretic hosts provide transport to fresh resources and
protection from unfavourable biotic and abiotic environments. Many species of
Rhabditida, Diplogasterida and Aphelenchida develop phoretic relation-ships but
few species of Tylenchida (Massey, 1974) and Strongylida are phoretic (Robinson,
1962). Formation of dauer juveniles (Sudhaus, 1976; Maggenti, 1981) and the
ability to nictate are a few examples of phoretic adaptations discussed in this
chapter. Such interactions are either facultative (e.g. synchronization of
Bursaphelenchus seani with helictid wasps, Giblin and Kaya, 1983) or obligate
(e.g. synchronization of Bursaphelenchus cocophilus with Rhynchophorus,
Giblin-Davis, 1993) depending upon behavioural adaptations. Antagonism, a varied
but interactive behaviour leading to nematode predation and parasitism, is
discussed in association with important natural enemies such as fungi, bacteria,
insects and nematodes (Stirling, 1991). Chapter 10 indicates that competition is
the basis for nematode responses such as co-existence, population fluctuation,
migration, spatial displacement, aggregation and sharing food resources.

Mary Barbercheck and Larry Duncan reviews nematode
responses to these chemical and physical challenges with emphasis on updating
and expanding topics treated by Croll (1970). The influence of many abiotic
factors on nematode activities has adaptive significance, as these influences
elicit responses such as acclimation and orientation. The reasons why such
adaptations are necessary in nematodes exposed to adverse physical conditions
are discussed. The authors emphasize that nematode sensitivity, tolerance and
response to the abiotic environment are keys to exploiting nematode behaviour
for the management of economically important species.

Gregorich et al. (2001) defined population dynamics as `the
numerical changes in population within a period of time,' whereas Lawrence
(1995) described it as `changes in population structure over a period of time'.
The former encompasses seasonal variations in nematode populations (Kendall and
Bluckland, 1971) whereas the latter includes population cycles (Goodman and
Payne, 1979). Chapter 12 (Population Dynamics'), contributed by Brian Boag and
Gregor Yeates, reflects both components in an expansive examination of behaviour
at the nematode population rather than at the individual level by focusing on
temporal and spatial pat-terns of migration. The authors explain non-uniform
distribution behaviour of nematodes in soils, sediments, and plant and animal
tissues. They also describe changes in behaviour during migration and
environmental conditions responsible for variations in populations and
migrations. For example, variation in vertical migratory behaviour (Boag, 1981)
is attributed to root distribution, soil type, moisture, temperature, etc.
(Yeates, 1980; Rawsthorne and Brodie, 1986; Young et al., 1998). Horizontal
migratory behaviour is suggested (Taylor, 1979) as a useful tool to detect and
estimate the size of nematode populations (Been and Schomaker, 1996), as well as
mechanisms of nematode aggregation (Goodell and Ferris, 1981). Migratory
behaviour deserves special attention with reference to infective soil stages
because these nematodes respond to host cues. The distance migrated may be a
function of some nematodes waiting passively for a host while others are
dispersers.

Like other organisms, nematodes have strategies
to resist adverse environmental conditions. Such strategies may have
behavioural, biochemical or morphological components but all three
have strong associations with each other. In Chapter 13 (Survival
Strategies'), David Wharton describes various behavioural approaches
nematodes employ to avoid or mitigate stress, including
synchronizing parasite life cycles with host availability or
migration (e.g. phoresy) to escape environmental extremes until
favourable conditions return. Other species develop a degree of
tolerance or resistance. These adaptive strategies enhance survival
under biological (food inadequacy, predation, pathogens and
competition), physical (temperature, desiccation, pressure and
radiation) or chemical (pH, osmotic stress, anoxia) stress. Wharton
explains how various tactics and mechanisms govern nematode
behaviour in challenging environments. The reasons for and
mechanisms of attaining resting, infective and dauer stages,
diapause and egg diapause, arrested development and delays in the
life cycles are elaborated in this chapter.

The
Microbial Challenge by Robert I. Krasner (ASM)
undergraduate text on human-microbe interactions. Provides an understanding of
the biology of the microbial world and its effects on daily life. Contains three
sections titled, challenges, meeting the challenges, and current challenges.
Topics include microbial diseases, biological warfare, and antibiotic
resistance. Full-color format.

Accessible and fascinating
The Microbial Challenge is on human‑microbe interactions, intended as a text
for use in undergraduate science courses. Designed to help students better
understand the biology of the microbial world and its effect on their lives,
this timely volume covers issues of vital importance, including biological
warfare and terrorism, antibiotic resistance, the global impact of microbial
diseases, and immunization.

A hybrid of microbiology and public health,
The Microbial Challenge empha­sizes the significance of microbes in everyday
living. Students are led to understand public health problems and are provided a
greater awareness of disease on a global scale through an examination of
microbial (infectious) diseases and their societal consequences, including
descriptions of some of the major microbial diseases through the ages, efforts
to meet the challenges raised by microbes, and public health measures of
protection and surveillance put in place to keep ever‑challenging microbes at
bay. The beneficial nature of microbes is also examined; they are vital to the
cycles of nature, play an important role in the food industry, and are
significant tools in biological research.

Richly illustrated with many photos from the author's
extensive personal collection taken during his numerous trips abroad,
The Microbial Challenge is ideal for students not majoring in science, for
allied health sciences courses, and for public health courses. It can also be
used as supplementary reading in standard microbiology and other biology
courses.

A Chronology of Microbiology in Historical Context
by Raymond W. Beck (AMS) This informative and absorbing chronology presents
events in the annals of microbiology in light of their historical context and
identifies those individuals who made these events happen. Beginning in the 3rd
millennium B.C. with citations of ancient medicine and diseases, the chronology
follows the development of microbiology and related sciences through the 18th
and 19th centuries and culminates with the explosion of discoveries in the late
20th century.

Environmental Microbiologyby Alan H. Varnum, photography by Malcolm G.
Evans (ASM) A reference for students and professionals in microbiology,
microbial science, and environmental science, combining basics of science with
recent advances, plus high-quality color photos. Interactions between the
environment and the dominant microflora are discussed, as are interactions
between the various components of microflora; however, emphasis is on
understanding principles. After an overview of environmental microbiology,
sections cover aquatic, terrestrial, and extreme environments, with chapters on
areas such as marine and freshwater environments, micro-organisms and higher
plants, and saline environments. Varnam is affiliated with the University of
North London, UK

Molecular Mimicry, Microbes, and Autoimmunity
edited by Madeleine W. Cunningham, Robert S. Fujinami (ASM) focuses
on studies that identify mimicry between infectious agents and host
molecules. The 18 papers examine the origins of the field, the
current status, and the new developments that could lead to a better
understanding of molecular mimicry and how infectious agents trick
the host immune system to turn against a particular organ or group
of organs in the human body. Topics include heart disease, Lyme
arthritis, diabetes, Chagas' disease, peptide mimicry of
streptococcal group A carbohydrate, peptide induction of systemic
lupus autoimmunity, and the role of T cells in mimicry and
determinant spreading.

Dictionary of Microbiology and Molecular Biologyby Paul Singleton,
Diana Sainsbury, 3rd edition (Wiley) covers pure and applied
microbiology, from taxonomy of algae, bacteria, fungi, protozoa and viruses to
microbiology associated with medicine, the food industry, plant pathology and
veterinary science. Microbiologically relevant aspects of molecular biology are
also included. Entries range from concise definitions to mini-reviews, many of
one page or more in length. This Third Edition has been extensively updated with
4,000 expanded and new entries and contains a total of 18,000 entries
all-together.

Unlike similar titles in this field
Dictionary of Microbiology and Molecular Biologysupplies references to
extend the range and usefulness of the dictionary. * A complex system of
internal cross-referencing links entries of related interest and allows topics
to be seen in a broader, interdisciplinary context. * Extensively updated with
4,000 expanded and new entries

Editor’s
summary: In writing this new edition of the Dictionary we had several aims in
mind. One of these was to provide clear and up‑to‑date definitions of the
numerous terms and phrases which form the currency of communication in modern
microbiology and molecular biology. In recent years the rapid advances in these
disciplines have thrown up a plethora of new terms and designations which,
although widely used in the literature, are seldom defined outside the book or
paper in which they first appeared; moreover, ongoing advances in knowledge have
frequently demanded changes in the definitions of older terms ‑ a fact which is
not always appreciated and which can therefore lead to misunderstanding.
Accordingly, we have endeavoured to define all of these terms in a way which
reflects their actual usage in current journals and texts, and have also given
(where appropriate) former meanings, alternative meanings, and synonyms.

A second ‑ but no less important ‑ aim was to encapsulate
and integrate, in a single volume, a body of knowledge covering the many and
varied aspects of microbiology. Such a reference work would seem to

be particularly useful in these days of increasing
specialization in which the reader of a paper or review is often expected to
have prior knowledge of both the terminology and the overall biological context
of a given topic. It was with this in mind that we aimed to assemble a detailed,
comprehensive and interlinked body of information ranging from the classical
descriptive aspects of microbiology to current developments in related areas of
bioenergetics, biochemistry and molecular biology. By using extensive
cross‑referencing we have been able to indicate many of the natural links which
exist between different aspects of a particular topic, and between the diverse
parts of the whole subject area of microbiology and molecular biology; hence the
reader can extend his knowledge of a given topic in any of various directions by
following up relevant cross‑references, and in the same way he can come to see
the topic in its broader contexts. The dictionary format is ideal for this
purpose, offering a flexible, `modular' approach to building up knowledge and
updating specific areas of interest.

There are other more obvious advantages in a reference work
with such a wide coverage. Microbiological data are currently disseminated among
numerous books and journals, so that it can be difficult for a reader

to know where to turn for information on a term or topic
which is completely unfamiliar to him. As a simple example, the name of an
unfamiliar genus, if mentioned out of context, might refer to a bacterium, a
fungus, an alga or a protozoon, and many books on each of these groups of
organisms may have to be consulted merely to establish its identity; the problem
can be even more acute if the meaning of an unfamiliar term is required. A
reader may therefore be saved many hours of frustrating literature‑searching by
a single volume to which he can turn for information on any aspect of
microbiology.

An important new feature of this edition is the inclusion of a large
number of references to recent papers, reviews and monographs in
microbiology and allied subjects. Some of these references fulfil
the conventional role of indicating sources of information, but many
of them are intended to permit access to more detailed information
on particular or general aspects of a topic ‑ often in mainstream
journals, but sometimes in publications to which the average
microbiologist may seldom refer. Furthermore, most of the references
cited are themselves good sources of references through which the
reader can establish the background of, and follow developments in,
a given area.